Control circuit for yarn clearing apparatus



Sept. 4, 1962 H. w. SCHNEIDER ETAL 3,052,826

CONTROL CIRCUIT FOR YARN CLEARING APPARATUS Filed Dec. 2. 1958 2Sheets-Sheet 1 INVENTORS Hana W- scnuzmzmand,

A E T C. Lasunours ATTORNEYS i B BY Se t. 4, 1962 H. w. SCHNEIDER ET AL3,052,326

CONTROL CIRCUIT FOR YARN CLEARING APPARATUS Filed Dec. 2, 1958 2Sheets-Sheet 2 Mama W- Summsz and.

ALBERT C. LEENHOUTS,

INVENTORQ- BY 01171), than, MAM M131 ATTORNEYS 3,952,326 CUNTROL CIRCUITFOR YARN CLEARING APPARATUS Henri W. Schneider and Albert C. Leenhouts,Enschede,

Netherlands, assignors to J. F. Scholten and Zonen,

N.V., Willenstad, Curacao, a corporation of Curacao,

Netherlands Antilles Filed Dec. 2, 1953, Ser. No. 777,632 Claims. (Cl.317-14?) This invention relates to apparatus for processing textilematerial such as yarn and the like and more particularly to electricallyoperated apparatus for detecting and providing for the elimination ofyarn portions representing undesirable extreme deviations in the mass ofthe yarn.

In the manufacture of textile material such as yarn and the like, it isfrequently desirable for the sake of yarn quality to remove certain yarnportions, the thickness or mass of which deviates to an excessive andundesirable extent from the mean or average mass deviations of the yarn.For instance, yarn portions which are considerably thicker are ofgreater mass than the average thickness or mass of the yarn and whichare relatively short in length are generally undesirable and arecommonly referred to in the textile industry as slubs. These slubs, asis well known, are caused by such factors as the incorporation of lint,fly, and similar unspinnable fibers in the yarn, broken filaments, orimproper drafting of the yarn as it is processed. As is well known,these slubs weaken and reduce the quality of the yarn and therefore mustbe eliminated when yarn of high quality is desired.

Many devices are available commercially for removing or cleaning theseslubs from yarn and are frequently referred to as slub catchers. Theseslub catchers may be broadly classified into two categories, namely themechanical type and the electrical type and it is to the electricallyoperated type of slub catcher that this invention is directed. A slubcatcher to which this invention is particularly applicable and of whichthis invention represents an improvement in the slub catcher shown inthe copending patent application of Hendrick Van Lingen et 211., SerialNo. 770,482, entitled Apparatus for the EX- amination of TextileThreads, filed October 29, 1958, and now abandoned. As discussed in thispatent application, the slub catcher, which is preferably mounted on awinder, is of the type which is provided with a measuring capacitorhaving spaced plates through which the yarn being wound is advanced at arelatively high speed. The variations in the thickness or mass of theyarn being wound are converted into an electrical signal orrepresentation and if an extreme mass deviation such as that produced bya slub generates a signal which exceeds a predetermined level ormagnitude, the slub catcher is operated so as to perform a controlfunction such as severing the yarn. The winder operator then cuts outthe slub and reties the yarn permitting the yarn to continue its advancethrough the slu-b catcher. As can be understood in such yarn clearingapparatus, the slub catcher is adjusted so as to operate only when toolarge a deviation from the average mass of the yarn is encountered astoo large a deviation would affect the quality of the fabric formed fromthe yarn.

Accordingly, as discussed in the above patent application, thesensitivity of the slub catcher is adjustable so that the extreme massdeviation in yarn at which the slub catcher will be actuated and performits control function may be readily predetermined. Therefore, not onlymust the sensitivity of the slub catcher be changed to predetermine theminimum slub mass required to actuate the slub catcher, but as the countor size of the yarn 3,052,826 Patented Sept. 4, 1962 being cleared ischanged, the sensitivity of the slub catcher must be changedcorrespondingly. This sensitivity adjustment is a precise undertakingand should be performed only by those persons thoroughly trained andskilled in this type of operation. Furthermore, even if satisfactoryskilled labor is obtained for performing this precise adjustment, thesubstantial number of slub catchers employed in the usual textile millmeans that considerable time and labor is involved in making theseadjustments each time the size of the yarn to be cleared is changed.

Another difiiculty which arises with the use of the elect-ricallyoperated type of slub catcher is the tendency of the slub catcher toperform the control function or, in other words, to cut the yarn as theyarn is being inserted within the plates of the measuring capacitor,particularly in the case where the slub catcher has been set for extremesensitivity. This inadvertent slub catcher actuation is a result of thesubstantial yarn mass change when the yarn is inserted within thecapacitor plates, and often the sensitivity of the slub catcher must betemporarily changed from the sensitivity setting at which the slubcatcher is to normally operate in order to permit the insertion of theyarn within the plates. Here again, a skilled operator is preferablyemployed to make this sensitivity change and even with a skilledoperator, the sensitivity may not be returned to its original setting asa result of human error and the like.

In another respect, electronic devices such as the electrically operatedslub catcher discussed in the above-mentioned patent application containcomponents which are very sensitive and their settings and values areextremely critical so that it is quite difficult if not impossible tocontinuously operate such devices without the presence of somevariations, however slight, which affect the accuracy of theirperformance.

For instance, as is well known, power source voltages frequentlyfluctuate, which change is in turn passed along to the circuitsconnected thereto. As voltage and current values are critical in many ofsuch circuit components, the performance of electronic circuits willcorrespondingly vary with these power source variations. Other factorshave been found to have influence on the performance of these slubcatcher electronic circuits one in particular being temperatureconditions and as these temperature conditions vary from time to timethe performance of the circuit components will vary correspondingly.Furthermore, it is not uncommon for circuit components such as vacuumtubes and the like to become Weak through use and thus change theiroperating characteristics over a period of time producing changes in theoperating characteristics of the circuit.

Accordingly, a primary object of the invention is to provide -a new andnovel control circuit for yarn clearing apparatus.

Another object of the invention is to provide a new and novel controlcircuit for yarn clearing apparatus which is self-adjusting for uniformclearing action on yarn of any size over a wide range.

Still another object of the invention is to provide a new and novel slubcatcher control circuit which automatically compensates for a change inthe size of the yarn being cleared to eliminate any need for adjustmentof the circuit after the desired slub clearing sensitivity has once beenestablished.

A further object of the invention is to provide a new and novel methodof uniformly clearing extreme mass deviations fom yarn over a wide rangeof yarn sizes.

A still further object of the invention is to provide a new and novelcontrol circuit for slub catchers of the electrically operated typewhich produces an electrical signal corresponding to yarn massvariations, which automatically compensates for signal variations causedby such uncontrollable factors as line voltage variations, temperaturefluctuations, and the like, and in which the slub catching actiondepends on the performance of passive elements such as resistors,capacitors and the like so as to be independent of any spontaneouschanges in the amplification of the signal.

This invention further contemplates the provision of a new and novelcontrol circuit for an electrically operated yarn clearing apparatuswhich continuously produces a comparison between the extreme mass yarndeviation and the mean or average mass or thickness deviation of yarnbeing examined so as to permit actuation of the slub catcher upon thepresence of a signal value which represents an undesirable extreme massdeviation and permits yarn of various sizes over a wide range to becleared of undesirable extreme mass deviations without the need ofadjustment when changing the size of yarn to be cleared.

Still another object of the invention is to provide a new and novelcontrol circuit for an electrically operated yarn clearing apparatus inwhich a suitable alarm or signal device is actuated when the yarn is notbeing examined and which prevents actuation of the yarn clearing actionwhen the yarn is initially placed into the examining position within theyarn clearing apparatus.

A further object of the invention is to provide a new and improved slubcatcher control circuit which is automatic in operation after an initialsensitivity setting and at the same time utilizes a minimum of parts, iscapable of operating over long periods of time without breakdown and ischaracterized by extremely accurate yarn examining action.

Briefly, the objects of the invention and other related objects areaccomplished by providing means for producing an electrical signal whichsignal varies in response to the variation in the mass or thickness inyarn being examined by yarn clearing apparatus. This variable orfluctuating signal which is preferably amplified is conducted afteramplification through first and second paths, the first of whichconducts the signal directly to relay means arranged to perform acontrol function. The second path for the signal includes means forconverting this fluctuating signal to a steady-state or non-variablesignal which reflects the average or mean variations in mass orthickness of the yarn. As is well known, the larger the size of theyarn, the greater the average mass deviations and consequently thegreater the value of this steady-state signal. This steady-state signalis also conducted to the relay means which is so arranged that thesteady-state signal inoperatively conditions the relay means and thesteady-state signal is reduced proportionally with an increase in thevalue of the fluctuating signal. If the variable signal reaches apredetermined extreme value, this extreme value corresponding to theabsolute value of the mass variation produced by a yarn mass or slub ofobjectionable size, to sufiiciently reduce or eliminate the steady-statesignal, the relay means is operatively conditioned and performs thecontrol function. In addition, means are provided in the circuit forpreventing the operation of the relay means by the variable signal inthe absence of the steady-state signal or when the steady-state signalproduced in the second path does not exceed a predetermined minimumvalue. Furthermore, an alarm device such as a lamp or the like may alsobe incorporated into the circuit so as to indicate the absence or thepredetermined low value of this steady-state signal in the second path.

Some of the objects of the invention having been stated, other objectswill appear as the description proceeds when taken in connection withthe accompanying drawings, in which:

FIGURE 1 is a wiring diagram of a control circuit for yarn clearingapparatus in accordance with the invention;

FIGURE 2 is a modification of the control circuit of FIGURE 1; and

FIGURE 3 is a second modification of the control circuit of FIGURE 1.

Referring now to FIGURE 1, there is shown a wiring diagram illustratingone embodiment of the novel control circuit of the invention. As hasbeen previously discussed, this control circuit is preferablyincorporated in yarn clearing or slub catching apparatus such as thatapparatus described and claimed in the Van Lingen et al. applicationreferred to above. The control circuit of the invention is arranged toreceive a continuous electrical signal which fluctuates or varies inaccordance with mass variations in the yarn being examined as the yarnis advanced at a relatively high speed.

Any conventional evice may be utilized with the control circuit ofFIGURE 1 for sensing the yarn mass variations such as devices whichoperate pneumatically, photoelectrically or by capacitive means. Asdescribed in the Van Lingen et al. application, the yarn to be clearedpasses between the spaced plates of a measuring capacitor which producesan electrical signal that varies in accordance with the variations inthe mass of the advancing yarn.

For the purpose of clarity, the mass change measuring deviceincorporated with the circuit of FIGURE 1 for generating thisfluctuating or variable signal has not been shown and it should beunderstood that the means described in the Van Lingen et al. applicationrepresent one convenient arrangement for producing an electrical signalwhich is a reflection or an electrical representation of the masschanges in the advancing yarn.

In the arrangement of the circuit of FIGURE 1, the variable orfluctuating signal produced is coupled by means of a capacitor 11 to thecontrol electrode or grid 12 of a triode 13 which contains a cathode 14and an anode or plate 16. A grid leak resistor 17 is connected to thegrid 12 and is connected to ground by means of a ground conductor 18.The triode 13, which is arranged to function as an amplifier, has itsplate 16 connected by means of conductor 19 to a source of positive DCvoltage B+ through resistors 29, 21. A movable tap 22 is associated withthe resistor 26 and is connected to a conductor 23 which constitutes afirst path for the signal generated by the mass variations in theadvancing yarn and amplified in the triode 13. In the embodimentillustrated, the amplified signal, although fluctuating in nature, has apositive value. Conductor 23 is connected through coupling capacitor 24,resistor 25, coupling capacitor 26 and resistor 27 to relay meansdesignated generally by the numeral 28.

In the specific embodiment illustrated, the relay means 28 comprise athyratron 29 and a coil 31 having associated therewith a core 32arranged to perform a control function such as the actuation of a yarncutting device in the manner described in the above refer-red to VanLingen et al. patent application. The resistor 27 is therefore connectedto the control electrode or grid 33 of the thyratron 29 which alsocontains a cathode 34 and a plate 37 connected by means of conductor 38to one side of the coil 31. The other side of the coil 31 is connectedto a suitable source of positive voltage B+.

A fixed negative bias voltage B- is fed to the grid 33 of the thyratron29 through a resistor 39 connected to the junction of resistor 27 andcapacitor 26. The value of the B- voltage is selected in accordance withthe characteristics of thyratron 29 and the circuit performance desiredas will be explained hereinafter.

A second path is provided for the amplified signal appearing in thetriode plate conductor 19 which comprises a conductor 41 connected toconductor 19 between the triode plate 16 and the variable resistor 26 asshown in FIGURE 1. Means have been provided in the circuit of FIGURE 1for converting or rectifying the amplified variable signal appearing atthe output of triode 13 to a steady state or non-variable signalreferred to herein after as the automatic bias voltage. Morespecifically, conductor 41 is connected by means of capacitor 42 to avoltage doubling circuit comprising a pair of diodes 43, 44- and acapacitor 47. The output of this voltage doubler appears across a loadresistor 48. As shown, the voltage doubling circuit is grounded byconnecting the junction of the cathode of diode 44, capacitor 47, andresistor 43 to the ground conductor 18.

The rectified output or automatic bias voltage of the voltage doublingcircuit appearing at the junction of resistor 48 and the plate of diode43 has a negative value and is fed by means of resistor 49, resistor 51and resistor 27 to the thyratron grid 33. A capacitor 52, one side ofwhich is grounded by conductor 13, is connected in the well known mannerto the junction of the resistors 49, 51 in order to smooth out theripple in the rectified signal produced by the voltage doubling circuit.It should be understood that the resistors 49, 51, 39 therefore form avoltage dividing system so that only approximately 80- 90% of the fullautomatic bias voltage appears on the thyratron grid 33.

The automatic bias voltage appearing on the junction of the plate ofdiode 43 and resistors 48, 49 is conducted by means of a resistor 53 tothe junction of resistor and the coupling capacitor 26 to which junctionis also connected to the plate of a clipper diode 54, the cathode ofwhich is suitably grounded. If a vacuum type clipper diode 54 isemployed rather than a crystal diode or semiconductor diode, theresistor 25 must be used for good clipping in order to provide a voltagedivider comprising the resistor 25 and the internal resistance of thevacuum clipper diode.

In many cases it is desirable that some signaling or indicating means beprovided for readily indicating that the yarn has been removed from themeasuring condenser or that no signal is being produced. Therefore,means have been provided in the circuit of FIGURE 1 for indicating theabsence of the automatic bias voltage which preferably comprise a triode58 having grid 59 connected to the junction of resistors 49, 51 andcapacitor 52. The cathode of the triode 58 is grounded and its plate isconnected through a gas-filled signal light or other suitable alarmdevice 61 to a source of positive voltage 13+,

In the operation of a yarn clearing device or slub catcher utilizing thecircuit of FIGURE 1, the suitably generated, fluctuating signal voltagewhich is coupled to the grid 12 of the triode 13 by means of thecapacitor 11 is amplified in the triode and is conducted through thefirst path comprising conductor 23, capacitor 24, resistor 25, capacitor26, resistor 27 to the thyratron grid 33. As has been explained, thispositive amplified signal voltage fluctuates or varies in accordancewith the mass variations in yarn advancing through a yarn examiningdevice such as the spaced plates of a measuring capacitor and iscontinuously fed to the thyratron grid 33. In addition, the amplitude ofthis signal may be adjusted by means of the tap 22 associated withresistor 20 which provides a means for predetermining the minimum sizeof the yarn mass variation which is necessary for actuation of the relaymeans 28.

The thyratron 29 may be of either the positive grid or negative gridtype but in the preferred embodiment, the thyratron is preferably of thenegative grid type and is arranged to ignite or conduct when thenegative bias on grid 33 is less than approximately two volts. Thethyratron 29 is therefore biased slightly more than two volts negativeby means of the fixed bias voltage B- applied through resistor 39 sothat the thyratron 29 does not conduct in the absence of an automaticbias voltage.

During normal operation, as the variable signal is conducted through itsfirst path, it is simultaneously conducted through its second path bythe conductor 41 and is rectified by means of the diodes 43, 44 togetherwith the associated components to provide an automatic bias voltagehaving a negative value which is fed to the thyratron grid 33 throughresistors 49, 51 and 27. As is well known in voltage doubling circuitsof the type illustrated, the amplitude of the output signal is furtherincreased after rectification. Therefore, in addition to the fixed biasvoltage B-, an automatic bias voltage, which is a reflection of theaverage or mean mass variations in the advancing yarn, is applied to thethyratron grid 33 to further bias the grid negatively. As has beenexplained, the original automatic bias voltage has been reduced slightly(10- 20%) prior to reaching the grid 33.

When the signal voltage fed through conductor 23 to the grid 33 reachesa magnitude, which of course may be regulated by the variable resistor20, sufiicient to overcome the automatic bias voltage, the thyratron 29will conduct and energize the relay coil 31 to perform the controlfunction.

As is well known, the average value of the mass variations in yarnincreases with increasing yarn size. As a result of the automatic biasvoltage produced in the circuit, this change in average mass variations,which occurs when the size of the yarn being examined is changed, isautomatically evaluated by the circuit so that the circuit isself-adjusting. In other words, when the size of the examined yarn isincreased, the average yarn mass variation and consequently theautomatic bias voltage increases requiring a greater extreme massvariation to fire thyratron 29 for the same tap setting on resistor 20.For any size yarn, therefore, the ratio of the extreme mass deviationsrequired to actuate the relay to the average value of these massvariations is approximately the same for the same setting on resistor20.

VVhen the relay 28 has performed the control function such as cutting ofthe yarn and the machine operator has eliminated the slu-b and retiedthe yarn, the absence of the automatic bias voltage can cause ignitionof the thyratron by a very weak positive pulse or signal. Such a signalmight be produced during the reinsertion of the yarn within the platesof the measuring capacitor. Therefore, it is highly desirable that thethyratron 29 be prevented from firing when the yarn is being insertedwithin the yarn examining device.

As is well known, the diode 54 will only conduct when the voltage on itsplate becomes positive and therefore as long as the negative automaticbias voltage is fed to the junction of the diode plate, the resistor 25,and the capacitor 26, the signal in conductor 23 would have to exceedthis automatic bias voltage before the diode 54 would conduct. Thiswould not be possible in the circuit of FIGURE 1, as the thyratron 29would ignite before the automatic bias voltage is exceeded by the signalon the plate of diode 54-, since the automatic bias voltage on grid 33is lower than the full automatic bias voltage as explained above.

When there is no yarn in the yarn examining or measuring device andconsequently zero automatic bias voltage at the junction, the positivesignal. fed to the thyratron grid 33 cannot rise above zero as anypositive signal voltage will immediately cause the diode 54 to conduct.Therefore, if a positive impulse appears in conductor 23 as a result ofthe insertion of the yarn in the measuring capacitor, diode 54 willconduct and no signal can get to the thyratron grid 33 to causeignition.

It should be understood that in FIGURE 1 there have been shown diodes43, 44, 54 and triode 13 of the vacuum type as they can be all includedin the same envelope of a commercially available tube. However, diodesof the crystal, semi-conductor, and other types may be employed ifdesired.

In addition, it is highly desirable that suitable means be provided toindicate that no yarn is present in the yarn clearing apparatus or thatthe yarn is no longer advancing to indicate to the operator or thesupervisor that the slub catcher is not operating. Means therefore havebeen provided with this invention for signaling the absence of theautomatic bias voltage which of course reflects the absence of advancingyarn.

More specifically, as shown in FIGURE 1, the grid 59 of the triode 58 isconnected to the junction of the resistors 49, 51 and capacitor 52 so asto receive the automatic bias voltage. In the absence of this automaticbias voltage, such as when there is no yarn in the slub catcher or whenthe slub catcher has cut the yarn and yarn no longer advances, there isno bias voltage on the triode grid 59 and the triode conducts causing acurrent flow through the gas-filled signal light 61. The light 61therefore glows to indicate the absence of the automatic bias voltage.It should be understood that any suitable type of signaling device maybe used such as an alarm or the like instead of the signal light 61.

If it is desired to only detect slubs above a certain length independentof mass, an RC filter may be located between the diode 54 and thecapacitor 26 to provide a time delay. Thus if the slub is so short thatthe signal produced by a momentary extreme mass deviation falls to zerobefore a predetermined time period has elapsed, the thyratron 29 willnot ignite.

As previously discussed, during normal operation, the mass variations inthe advancing yarn produce a signal from which an automatic bias voltageis obtained which is fed to the grid 33 of the thyratron 29 and thisnegative bias voltage must be overcome by a positive signal having amagnitude representing an undesirable extreme mass deviation in the yarnwhich is to be removed. In many cases, it is not only desirable toprevent actuation of the slub catcher in the absence of yarn in themeasuring condenser or a termination of the yarn advance but also whenthe automatic bias voltage becomes relatively Weak or drops below apredetermined critical value permitting a relatively weak positiveimpulse or signal to ignite the thyratron.

In the circuits of FIGURES 2 and 3, there are shown modifications of theembodiment of FIGURE 1 which include means for preventing ignition ofthe thyratron when the automatic bias voltage falls below a certainvalue or is totally absent. It should be understood that in FIG- URES 2and 3 like numerals have been employed to identify like parts.

Referring now to FIGURE 2, diode '54, resistors 25, 39, 53 and capacitor26 included in FIGURE 1 have been eliminated and the variable signalconducted through the first path by conductor 23 is not clipped. Thevariable positive signal in conductor 23 is fed through capacitor 24 andresistor 27 to the grid 33 of thyratron 29. Furthermore, in the circuitof FiGURE 2, the fixed B- bias voltage is brought in through a conductor65 connected to the junction of capacitor 47 and resistor 48. An A.C.path to ground for the voltage doubling circuit is provided by acapacitor 67 having one side connected to the junction of the capacitor47 and resistor 48 and grounded on the other side by means of groundconductor 13.

A conductor 68 is connected to the junction of resistors 49, 51 andcapacitor 52 so that the automatic bias voltage is fed continuously tothe grid 69 of a triode 71 having a grounded cathode 72 and a plate '73.The characteristics of the triode 71 are selected so that if theautomatic bias voltage exceeds a predetermined minimum value the triodedoes not conduct. Therefore, if the automatic bias voltage falls belowthis minimum value or is completely eliminated, the triode 71 willconduct.

The plate 73 of triode 71 is connected by means of conductor 74 throughserially connected resistors 76, 77 to a source of positive voltage B+.A signal light 78 is connected in parallel with resistor 77.

A voltage divider circuit comprising serially connected resistances 79,81 is connected at one end to conductor 74 between resistor 76 andtriode plate 73 and at the other end to a negative voltage source B. Atap comprising a conductor 82 is connected at a point between theresistor 79 and resistor 81 and leads electrically to a controlelectrode 83 in the thyratron 29. A clipping diode 84- and a time delaycapacitor 86, connected in electrical parallel relationship, areconnected at one common side to tap conductor 82 between resistor 79 andthe control electrode 83 and at their other side to the ground conductor18.

In the absence of an automatic bias voltage on the triode grid 69 or ifthe voltage falls below a critical value, the triode 71 conducts and alarge current flows through resistors 76, 77. The voltage drop acrosresistor 77 will energize signal light 78 to indicate very little or nobias voltage is present. The high current in conductor 74 produces a lowplate voltage on triode 71 as a result of the voltage drop in resistors76-, 7'7 and the tap 82 between the voltage dividing resistors 79, 81will therefore produce an even lower negative voltage on the controlelectrode 83 of thyratron 2,9 preventing its ignition.

Thus, in the absence of an automatic bias voltage or when the automaticbias voltage becomes too low, ignition of the thyratron cannot takeplace. When the automatic bias voltage has been built up again undernormal yarn examining conditions, the bias voltage on grid 69 cuts offtriode 71 and there is no current flow through conductor 74. The voltageon the thyratron electrode 83 therefore tends to go positive but cannot,as any positive voltage on conductor 82 results in a current flowthrough diode 84, and prevents the buildup of any positive voltage onthe electrode 83 which would prevent actuation of the thyratron 29 undernormal operating conditions. The capacitor 86 in parallel with the diode84 supplies a small time delay.

Referring now to FIGURE 3, a second modification of the control circuitor" FIGURE 1 is shown and as in FIGURE 2 like numerals are used toidentify like parts. Instead of the triode 71 of FIGURE 2, a gas-filledtube 91 is employed in which the grid voltage for firing the tube ismore sharply defined. The tube '91 contains a grid 92 connected by meansof conductor 93 to the junction of resistors 49, 51 and capacitor 52 forconducting the generated automatic bias voltage to the grid.

The electron tube 91 has a cathode 94 grounded by means of conductor 96to the ground conductor 18. The plate 97 of tube 91 is connected bymeans of resistors 98, 99 to two voltage sources, one a positive D.C.voltage 13+, preferably twenty-five volts, and the other a relativelyhigh A.C. voltage of normal line frequency which is preferablyapproximately 250 volts. A signal light 101 of the type discussed aboveis preferably connected in parallel with resistor 98.

In order to obtain the above described ignition blocking action inthyratron 29, a pair of serially connected resistor-s ill-2, 193 areconnected at one end to the junction of resistor 98 and the plate '97 oftube 91 and at their other end to the thyratron control electrode 83.The diode 84 is connected at one side to the junction of resistor 103and control electrode 83 in parallel with capacitor 86 which isconnected at its corresponding side to the junction of resistors 102,103. As in the embodiment of FIGURE 2, capacitor 86 and diode 84- aregrounded by means of the ground conductor 18.

Under normal operating conditions during yarn examination, the automaticbias voltage cuts off the gas-filled tube 91 and the voltage on theplate of tube 91 will be approximately twenty-five volts as determinedby the B+ voltage. This voltage would also appear on the thyratroncontrol electrode 83 but the diode 84 conducts when the voltage onelectrode 83 tends to go positive so that when the automatic biasvoltage is present, the voltage on the electrode 83 remains Zero. TheAC. voltage fed into the circuit through resistor 99 is at this timefiltered out by a simple ripple filter arrangement utilizing thecapacitor 86.

In the absence of the automatic bias voltage, the gasfilled tube 91conducts and rectifies the AC. voltage so that negative impulses onlyare produced in a manner of a half-wave rectifier and these negativepulses are smoothed out by the capacitor 86. This smoothed out,rectified negative voltage exceeds the 13+ voltage and the controlelectrode 83 goes negative preventing ignition of the thyratron 29.During this action, the signal light 101 is energized and glows toindicate that the automatic bias voltage is too low or is totallyabsent. As in the control circuit of FIGURE 2, capacitor 86 provides atime delay of a small amount in addition to smoothing out the negativepulses produced during the half cycle when tube 91 conducts.

It can be seen therefore that there has been provided with thisinvention a new and novel control circuit for yarn clearing apparatuswhich eliminates many manual operations previously required and permitsthe operation of yarn clearing apparatus with a greater degree ofaccuracy than heretofore possible and with a minimum amount of time. Oneof the outstanding features of this invention is the feature of the slubcatching apparatus which permits it to automatically adjust to any sizeyarn which is to be cleared or cleaned of slubs. Once a sensitivitysetting has been made on the slub catcher for the minimum extrem massdeviation which the slub catcher is to pass, no further adjustment isrequired and the slub catcher will automatically examine various yarnsizes over a wide range with the same relative sensitivity without theneed for additional adjustment. Furthermore, this slub catching actionor sensitivity is completely independent of the amplification of thegenerated signal so that temperature fluctuations, changes in linevoltage, and similar unpredictable factors which affect theamplification of the signal no longer affect the detecting or examiningaction of the slub catcher, as this examining action now depends only onsuch passive elements as resistors, condensers and the like. Furthermorethe novel arrangement of the circuit permits the use of the very simpleand quite inexpensive A.C. amplification techniques rather than D.C.amplification common to presently employed yarn irregularity detectioninstruments. Although the control circuits of the invention have beendescribed in combination with a slub catcher which provides for severingthe yarn when a slub appears to permit removal of the slub by anoperator, the circuits may be similarly employed to actuate a counter orthe like in order to totalize the number of yarn faults or slubs withoutcutting or stopping the movement of the advancing yarn. In this manner,yarn quality control may be practiced with a high degree of accuracy.

Another outstanding feature of the invention is the method of yarnexamination which can be practiced with the novel circuit of theinvention. As discussed above, this novel method involves comparing themean or average mass deviations in yarn with the absolute or total massdeviation so that a ratio is obtained which is maintained substantiallyuniform throughout changes in the size of the yarn being examined. As iswell known, this method takes advantage of the inherent increase inaverage yarn mass deviations as the yarn size is increased.

Another feature of the invention is the automatic signaling device whichindicates that the yarn has been removed from the yarn examining deviceincorporated in the yarn clearing apparatus so that not only are theoperators immediately notified when the yarn is cut but any attempt toremove the yarn from the yarn examining device and thus increase theoutput without improving the quality of the yarn by an operator may beimmediately detected.

In the drawings and specification there has been set forth a preferredembodiment of the invention and, although specific terms are employed,they are used in a generic and descriptive sense only and not (forpurposes of limitation, the scope of the invention being defined in theclaims.

We claim:

1. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,means for producing from said variable electrical signal a steady-stateelectrical signal corresponding to the average value of the variationsin the mass of said yarn, relay means for performing a control function,means for conducting said variable signal and said steady-state signalto said relay means for oppositely conditioning said relay means wherebya predetermined amplitude of said variable signal corresponding to anexcess variation in the mass of said yarn operatively conditions saidrelay means to perform said control function.

2. A control circuit for yarn clear-ing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,means for producing a steady-state electrical signal from said variablesignal corresponding to the average variations in the mass of said yarn,relay means for performing a control function, means for conducting bothsaid variable signal and said steady-state signal to said relay meanswhereby said steadystate signal inoperatively conditions said relaymeans and the value of said steady-state signal is reducedproportionally with the amplitude of said variable signal, said relaymeans being arranged to operatively respond and perform said controlfunction at a predetermined reduction of said steady-state signal by avariable signal corresponding to an excessive variation in the mass ofsaid yarn.

3. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,relay means for performing a control function, means for simultaneouslyconducting said variable signal through a pair of paths connected tosaid relay means, means in one of said paths for converting saidvariable signal to a steady-state electrical signal corresponding to theaverage value of the variations in the mass of said yarn and whichinoperativeiy conditions said relay means, said variable signal in theother path being arranged to reduce the value of said steady-statesignal in proportion to the amplitude of said variable signal wherebysaid relay means operatively responds and performs said control functionat a predetermined reduction of said steady-state signal by a variablesignal corresponding to an excessive variation in the mass of said yarn.

4. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,relay means for performing a control function, a first path forconducting said variable signal to said relay means, a second path forsaid variable signal including means for converting said variable signalto a steady-state electrical signal corresponding to the average valueof said variations in the mass of said varn, said second path beingarranged to conduct said steady-state signal to said relay means forinoperatively conditioning said relay means, said variable signal beingarranged to reduce the value of said steadystate signal in proportion tothe amplitude of said variable signal whereby said relay meansoperatively responds :and performs said control function at apredetermined reduction of said steady-state signal by a variable signalcorresponding to an excessive variation in the mass of said yarn.

5. A control circuit for yarn clearing apparatus in accordance withclaim 4 including means for indicating the drop of said steady-statesignal said second path to 'a predetermined level.

6. A control circuit for yarn clearing apparatus in ac-- cordance withclaim 4 including means for preventing the actuation of said relay meanswhen the steadystalte signal in said second path drops to apredetermined level.

7. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,means for amplifying said variable signal, relay means for performing acontrol function, a first path for conducting said amplified variablesignal to said relay means, a second path for said amplified variablesignal including means for converting said amplified variable signal toa steady-state electrical signal corresponding to the average value ofthe variations in the mass of said yarn, said second path being arrangedto conduct said steady-state signal to said relay means forinoperatively conditioning said relay means, said amplified signal beingarranged to reduce the value of said steady-state signal in proportionto the amplitude of said amplified variable signal whereby said relaymeans operatively responds and performs said control function at apredetermined reduction of said steady-state signal by an amplifiedvariable signal corresponding to an excessive variation in the mass ofsaid yarn.

8. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously produc ing a variable electricalsignal corresponding to the variations in the mass of advancing yarn, asource of power, relay means for performing a control function, saidrelay means including an electron tube, said electron tube having atleast three electrodes including a control electrode, a first path forconducting said variable signal to said control electrode, a second pathfor said variable signal including mean-s for rectifying said variablesignal to a steady-state electrical signal of opposite polarity fromsaid variable signal corresponding to the average value of saidvariations in the mass of said yarn, said second path being arranged toconduct said steady-state signal to said control electrode for biasingsaid electron tube to a nonconduotive condition, said variable signalbeing arranged to reduce the value of said steady-state signal inproportion to the amplitude of said variable signal whereby saidelectron tube conducts and actuates said relay means to perform saidcontrol function at a predetermined reduction of said steady-statesignal by a variable signal corresponding to an excessive variation inthe mass of said yarn.

9. A control circuit in accordance with claim 8 including a fixed DC.voltage source, means connecting said fixed DC. voltage source to saidcontrol electrode whereby said DC. voltage biases said electron tubeinto a non-conductive condition.

10. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal having a positive polarity corresponding to the variations in themass of advancing varn, relay means for performing a control function, afirst path for conducting said variable signal to said relay means, asecond path for said variable signal including means for rectifying saidvariable signal to a negative DC signal having a value corresponding tothe average value :of said variations in the mass of said yarn, saidsecond path arranged to conduct said DC. signal to said relay means inopposition to said positive variable signal and maintain said relaymeans in an inoperative condition whereby a variable signal ofpredetermined positive amplitude couresponding to an excessive variationin the mass of said yarn sufficient to reduce said DC. signal to apredetermined level operatively conditions said relay means to performsaid control function.

11. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,relay means for performing a control function, a first path forconducting said variable signal to said relay means, a second path forsaid variable signal including means for converting said variable signalto a steady-state electrical signal corresponding to the average valueof said variations in the mass of said yarn, said second path beingarranged to conduct said steady-state signal to said relay means forinoperatively conditioning said relay means, said variable signal beingarranged to reduce the value of said steadystate signal in proportion tothe value of said variable 12 signal, means for clipping said variablesignal in said first path in the absence of said steady-state signal,said relay means being arranged to operatively respond and perform saidcontrol function at a predetermined reduction of said steady-statesignal by a variable signal corresponding to an excessive variation inthe mass of said yarn.

12. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,first relay means for performing a control function, a first path forconducting said variable signal to said relay means, a second path forsaid variable signal including means for converting said variable signalto a steady-state electrical signal corresponding to the average valueof said variations in the mass of said yarn, said second path beingarranged to conduct said steady-state signal to said first relay meansfor inoperatively conditioning said relay means, said variable signalbeing arranged to reduce the value of said steady-state signal inproportion to the amplitude of said variable signal, said first relaymeans being arranged to operatively respond and perform said controlfunction at a predetermined reduction of said steady-state signal by avariable signal corresponding to an excessive variation in the mass ofsaid varn, second relay means operatively associated with said firstrelay means, a third path for conducting said steady-state electricalsignal to said second relay means for inoperatively conditioning signalexceeds a predetermined minimum level, said second relay means beingarranged to operatively respond when said steady-state signal fallsbelow said predetermined level and prevents actuation of said firstrelay means.

13. A control circuit in accordance with claim 12 wherein said secondrelay means comprises a triode, said triode being arranged to conductwhen said steady-state signal falls below said predetermined level andprevent actuation of said first relay means.

14. A control circuit in accordance with claim 12 wherein said secondrelay means include a gas-filled electron tube, a source of AC. voltageconnected to said gas-filled tube and to said first relay means, saidgas-filled electron tube being arranged to conduct and rectify said AC.voltage when said steady-state signal falls below said predeterminedlevel and provide a negative DC. voltage for preventing actuation ofsaid first relay means.

15. A control circuit for yarn clearing apparatus comprising, incombination, means for continuously producing a variable electricalsignal corresponding to the variations in the mass of advancing yarn,means for amplifying said variable signal, said amplified variablesignal having a positive polarity, means for adjusting the signal gainin said amplifying means, a source of power, relay means for performinga control function, said relay means including a thyratron forconnecting said relay means to said source of power, said thyratronhaving at least three electrodes including a control electrode, a sourceof negative DC. bias voltage, means for conducting said negative DC.bias voltage to said control electrode for biasing said thyratron into anon-conductive condition, a first path for conducting said amplifiedvariable signal to said thyratron control electrode, a second path forsaid amplified variable signal including a voltage doubling circuit forrectifying said amplified variable signal to a DC. signal of negativepolarity corresponding to the average value of the variations in themass of said yarn, said second path being arranged to conduct said DC.signal to said thyratron control electrode for additionally biasing saidthyra-tron into said non-conductive condition, said amplified variablepositive signal being arranged to reduce the value of said DC. signal inproportion to the amplitude of said variable signal whereby saidthyratron conducts and actuates said relay means to perform said controlfunction When said DC. signal is overcome by a variable signalcorresponding to an excessive variation in the mass of said yarn, meansincluding an indicator light for indicating the drop of said DC. signalin said second path to a predetermined low level, an electron tubeoperatively associated with said thyratron, a third path for conductingsaid DC signal in said second path to said electron tube whereby saidelectron tube conducts and inoperatively conditions said thyratron whensaid DJC. signal in said second path falls below a predetermined minimumvalue.

References Cited in the file of this patent UNITED STATES PATENTSFOREIGN PATENTS Great Britain Apr. 10, 1957 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No, 3,052,826 September 4, 1962 HenriW. Schneider et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 23, after thicker" insert or column 2, line 68, for "fom"read from column 12, line 28, after "conditioning" insert said secondrelay means when said steady-state electrical"; line 32, for "prevents"read prevent Signed and sealed this 5th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer v Commissioner ofPatents UNITED STATES PATENT OFFICE f CERTIFICATE OF CURRECTION PatentNo, 3,O52 826 September 4, 1962 Henri W. Schneider et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 1, line 23, after thicker insert or column 2 line 68, for "form"read from column 12, line 28, after "conditioning" insert said secondrelay means when said steady-state electrical"; line 32, for "prevents"read prevent Signed and sealed this 5th day of March 1963.

(SEAL) Attest:

ESTON G. JOHNSON DAVID L. LADD Attesting Officer S Y Commissioner ofPatents

